Systems of Measuring Kinship Degree

Most bilateral kinship systems and some unilineal ones make essential
distinctions between relatives on the basis of kinship distance for
purposes of assigning group membership, determining inheritance and
succession rights, and organizing other important social events and
interactions. In many cases these distances are assigned whole numbers
known as kinship degrees. While a single self-evident system for
assessing these quantities might be desirable, several different measures
have been developed. For example, Western kinship
degree calculations have varied historically and geographically between
the Roman or civil system and the Germanic or canon system, which is
currently the standard both in Catholic church regulations and English
common law.

Basic Kinship Numbers and Calculations

As many as six separate systems of caluculating kinship degree have been
proposed by various jurists, geneticists, and anthropologists. All are
ultimately based on simple systems of counting links between relatives
with reference to their most recent common ancestor. Circles of
kinship are often defined in terms of the ambiguous measure of "cousin
range".
More precise systems include: